Assigning data for storage based on speed with which data may be retrieved

ABSTRACT

A method, system, and apparatus for improving performance when retrieving data from one or more storage media. Files to be stored on the one or more storage media are classified into a ranking of different sets. Differences in retrieval value of different regions of the one or more storage media are exploited by selecting which files to store in which regions. For example, files that have a higher classification are stored in regions with faster retrieval values. The files can be classified based on frequency of access. Thus, files that are more frequently accessed are stored in regions that have a faster retrieval value. The files can be classified by another measure such as priority. For example, the classification for some or all of the files can be based on user-assigned priority. The classification may be based on events or data grouping.

FIELD OF THE INVENTION

The present invention relates to accessing data on one or more storagemedia. In particular, the present invention relates to improvingperformance when reading one or more storage media by assigninglocations for stored files based on a file classification and retrievalvalue of the data associated with particular regions of the one or morestorage media.

BACKGROUND

For many different types of storage media, the speed with which data maybe retrieved varies depending upon where the data is stored on thestorage medium. For example, with hard disk drives the retrieval valuevaries based on physical factors such as seek time, rotational delay,and disk transfer rate. Examples of other storage media for whichretrieval value differs based on where the data is stored include,hybrid drives (storage media have rotating platters as well as a solidstate component such as a flash component that can store data), andnetwork attached storage such as iSCSI. The retrieval value may beaffected by factors other than the physical characteristics of thestorage medium, such as the communication link, or network (if used).

Many manufactures of storage media provide information that roughlydescribes how fast the storage media will provide data. For example, amanufacturer may provide an “average access time”. In practice, the term“average access time” is used to describe how fast a storage medium is.A storage medium with a lower average access time is generally moreresponsive and “peppier” than one with a higher average access time. But“average access time” is just an average for the whole storage medium.The results may vary for individual accesses to data stored in differentlocations on that same storage medium. Moreover, manufacturers may quoteinternal disk transfer rates (the rate that data can be written to orread from the disk) as a range of values. For example, a range might bea minimum of 43 Mbytes per second and a maximum of 78 Mbytes per second.However, the actual transfer rate at any particular place on the diskmay be anywhere between the two extremes.

Thus, the actual speed with which data can be read from a storage mediumis difficult or impossible to know based solely on manufacturerspecifications. Moreover, factors external to the storage medium affectthe rate at which data can be retrieved from a storage medium. Forexample, if a host computer system is connected to one storage mediumvia a network (“network storage medium”) and another directly via a SCSIcable (“SCSI storage medium”), the retrieval value for the networkstorage medium may on average be slower than the SCSI storage medium.However, some regions of the network storage medium may have a fasterretrieval value than some regions of the SCSI storage medium.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1A is a diagram that illustrates an architectural overview of filepositioning, in accordance with a first embodiment of the presentinvention.

FIG. 1B is a diagram that illustrates an architectural overview of filepositioning, in accordance with a second embodiment of the presentinvention.

FIG. 2 is a flowchart illustrating steps of a process of determiningpositioning for files on one or more storage media, in accordance withan embodiment of the present invention.

FIG. 3 is a flowchart illustrating steps of a process of categorizingfiles by frequency of access and age, in accordance with an embodimentof the present invention.

FIG. 4 depicts a process of setting the size of each volume region andaccess frequency criteria, in accordance with an embodiment of thepresent invention.

FIG. 5 is a block diagram that illustrates a computer system upon whichan embodiment of the invention may be implemented.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however,that the present invention may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to avoid unnecessarily obscuring thepresent invention.

General Overview

A method, system, and apparatus are described herein for improvingperformance when reading one or more storage media. Files to be storedon the one or more storage media are classified into a ranking ofdifferent sets. The term file, as used throughout this description, isused to mean a file or a portion of a file. Differences in retrievalvalues of the data, based on where the data is stored on one or morestorage media are exploited by selecting which files to store in whichregions. By “retrieval value” of a particular location on a storagemedium it is meant a time or other value that represents the time ittakes to retrieve data from the particular location on the storagemedium. As an example, retrieval values may be determined by measuringthe difference between the time at which a host process issues a commandto access data from a storage medium and the time at which the data isavailable to the host process. Thus, the retrieval value may factor inthe time to transfer data and commands between a host computer systemand the storage medium. However, retrieval values can be determined inother ways. For example, in some circumstances a retrieval value couldbe the difference between the time at which the storage medium receivesa command to read data at a particular location and the time at whichthe storage medium outputs data for the location.

The retrieval value may be a value that approximates the time it takesto retrieve data from the storage medium. However, the retrieval valuecould be a relative ranking between two regions. For example, it couldbe determined that data can be retrieved faster from region 1 thanregion 2, without determining or estimating a time to retrieve data foreither region.

Files that have a higher classification are stored in a region that ischaracterized by a higher retrieval value. The files can be classifiedbased on frequency of access. Thus, files that are more frequentlyaccessed may be stored in a region that has a faster speed ofretrievability. The files can be classified by another measure, such aspriority. For example, the classification for some or all of the filescan be based on user-assigned priority. Other ways in which files can beclassified include events, such as a system boot. A still further way inwhich files can be classified is data grouping. An example of datagrouping is storing the files in a manner that reflects the way theyappear in a folder on the host computer system.

In accordance with an embodiment of the present invention, a retrievalvalue for each of a plurality of locations of the one or more storagemedia is accessed. A classification is formed for files that arecurrently stored or may be stored on the one or more storage media inthe future. For example, files may be classified based on frequency ofaccess. At least some of the files are stored on the one or more storagemedia based on the classification and the retrieval value of thelocations. The storing of the files may include moving a particular filefrom a location having a given retrieval value to another locationhaving a different retrieval value, or storing to the one or morestorage media a file that does not currently exist on the one or morestorage media.

In accordance with one embodiment, the one or more storage media isdivided into regions according to the retrieval values. A particularregion comprises one or more of the locations. The regions are rankedbased on the retrieval value for the locations of each particularregion. For example, one of the regions may be characterized as a fastregion because the locations in that region have fast retrieval time.Another of the regions may be characterized as a slow region because thelocations in that region have slow retrieval time. The files are storedin one of the regions, based on the ranking of the regions and theclassification of the files. For example, files that are accessed morefrequently are stored in the fast region.

Architectural Overview

FIG. 1A is a diagram that illustrates an architectural overview of filepositioning, in accordance with a first embodiment of the presentinvention. The retrieval value data 125 describes retrieval valuecharacteristics of the one or more storage media 120. The retrievalvalue is based, at least in part on, an internal disk transfer rate, inaccordance with an embodiment of the present invention. As usedthroughout this description, the term “internal disk transfer rate”means the rate at which a hard disk drive can transfer data between theplatters and the hard disk's controller. However, the retrieval valuemay be based on other factors, as well. For example, the retrieval valuemay be based on access time and factors external to the storage medium.As used throughout this description, the term “access time” means thetime from when a command to access the storage medium is received by thestorage medium until the storage medium is ready to read the data fromthe storage medium. External factors include, but are not limited to,communication links, networks (LANs, WANs, Internet, etc.), hostoverhead. The retrieval value data 125 may have a table with a columnfor location and a column for retrieval time. The location can beexpressed as a logical cluster number (LCN). This LCN may correspond tomultiple sectors of the one or more storage media 120. The locationmight be on a platter of a hard disk drive, but could be anotherlocation. For example, some storage media have rotating platters as wellas a solid state component such as a flash component that can storedata.

The file positioning engine 110 generates retrieval time based dividingdata 115, based on the retrieval time data 125. The retrieval time baseddividing data 115 describes how the one or more storage media 120 islogically divided into regions that are characterized by differentretrieval values. The storage medium retrieval value is not necessarilyuniform in a given region. For example, a particular storage mediummight have 20 or more different retrieval values, but the storage mediummight only be logically divided into three or four regions. Thus, thereis not necessarily a single storage medium retrieval value for aparticular region. However, the various regions can be characterized bythe fastest or slowest storage medium retrieval value in the region orsome statistical measure such as mean or medium storage medium retrievalvalue. The regions can then be ranked from a region characterized by thefastest storage medium retrieval value to a region characterized by theslowest storage medium retrieval value.

The retrieval time based dividing might also define a single region witha continuum of storage medium retrieval values. This region may becharacterized as having a first point with a fast storage mediumretrieval value and a second point with a slow storage medium retrievalvalue, with storage medium retrieval values decreasing between the firstpoint and the second point.

The file positioning engine 110 accesses retrieval time data 125 and thefile classification data 130 in order to determine where files should bestored on the one or more storage media 120. The file classificationdata 130 may describe how frequently each file is accessed. Thefrequency may be broken down by how often the file was accessed overdifferent periods of time. For example, file classification data 130 maydescribe the number of accesses over the last week, the number ofaccesses over the last month, etc. The file classification data may alsodescribe a relative priority of files. For example, a user or softwareprogram may assign a priority to files. As a particular example, filesof a certain type or associated with a given folder may be assigned ahigh priority. The file classification data may also be based on events.Still a further way to classify files is based on data grouping.Moreover, files can be classified based on any combination of accessfrequency, events, data grouping, or other factors.

FIG. 1B is a diagram that illustrates an architectural overview of filepositioning, in accordance with a second embodiment of the presentinvention. The retrieval value measurement component 140 determines theretrieval values of various regions of the one or more storage media120. In FIG. 1B, one of the storage media is depicted as accessible vianetwork 175. The network 175 includes, but is not limited to Local AreaNetworks LANs, Wide Area Networks (WANs), and the Internet. Thus, theretrieval value measurement component 140 determines the affect thenetwork 175 has on retrieval values, in this embodiment.

The file frequency access monitor 150 determines frequency of fileaccesses and provides file frequency access information to the filepositioning engine 110. The file priority information 160 describes apriority given to one or more of the files. For example, a user mayassign a priority to a file or group of files. The file positioningengine 110 inputs the file priority information. The event detection 180detects events that may be used by the file positioning engine 110 toclassify files. The file grouping information 190 is input to the filepositioning engine 110. Based on the file frequency access information,events, file groupings and/or the file priority information, the filepositioning engine 110 classifies the files. Based on the fileclassification and the retrieval time information, the file positioningengine 110 determines where to place files on the one or more storagemedia 120.

Process Flow

FIG. 2 is a flowchart illustrating steps of a process 200 of determiningpositioning for files on one or more storage media, in accordance withan embodiment of the present invention. Process 200 will be describedwith reference to various components in the architectures of FIG. 1A andFIG. 1B. However, process 200 is not limited to either architecture. Instep 202, a retrieval value is accessed for a number of differentlocations of one or more storage media. In one embodiment, the retrievalvalue is measured for various locations.

In one embodiment, the retrieval time is determined by a process on ahost computer system issuing read commands to various locations on theone or more storage media and determining a value that represents thetime to retrieve data from particular storage locations. However, adifferent technique may be used to determine retrieval times. Note thatthe retrieval time is not necessarily a time invariant. For example, ifthe storage medium is accessed via a network, then the retrieval timemay be affected by network traffic. The retrieval time is determinedbased on on-going monitoring of network traffic, in one embodiment.

The retrieval time takes into account substantially all the factors thatmay be involved in the retrieval time of a particular storage medium, inone embodiment. For example if a volume is made up of several networkattached storage devices, the network speed and latency is automaticallyincluded in the retrieval time (for example iSCSI). The solid stateportion of a hybrid drive's retrieval times can also be determined inrelation to its traditional rotating platter.

In one embodiment, internal disk transfer rate information is collectedor determined. Retrieval value is affected by internal disk transferrate. However, it is not necessary to determine or know the internaltransfer rate to determine the retrieval value. If a storage medium wereto provide internal disk transfer rate information in response to arequest to the storage medium, a request for the internal disk transferrate information can be sent to the storage medium. However, the storagemedium may not provide such information via a request. In oneembodiment, the internal disk transfer rate information is determined byissuing multiple read commands to the storage medium and measuringresponse time. A technique for determining internal disk transfer rateis described in U.S. Patent Application entitled “Online Storage MediumTransfer Rate Characteristics Determination”, to Kleinschmidt Jr. etal., Attorney Docket Number 60144-0014, filed on Jul. 28, 2006, andincorporated by reference in its entirety as if fully set forth herein.The internal disk transfer rate information may be accessed from a tablethat describes storage medium transfer rates characteristics for one ormore different storage media. For example, storage medium transfer ratecharacteristics may be obtained for different hard disk drivemanufactures/models in any fashion. These internal disk transfer ratecharacteristics can be stored in a table that is accessible to the filepositioning engine, wherein step 202 comprises accessing such a table.

Step 204 is the optional step of logically dividing the storage mediuminto regions according to the retrieval values. Each particular regioncomprises one or more of the locations, and the regions are ranked basedon the retrieval value for the locations of each particular region. Forexample, the storage medium might be divided into a region havinglocations with fast retrieval values, a region having locations withmedium retrieval values, and a region having locations with slowretrieval values. The storage medium can be logically divided into anynumber of regions. In one embodiment, rather than dividing the storagemedium into a number of regions, the storage medium is defined having arange of retrieval values from a fast retrieval value to a slowretrieval value. Thus, a single region of the storage medium can bedefined to have a continuum of retrieval values.

In general, the storage medium is logically divided into n-regions basedon retrieval values. For illustrative purposes, the following example oflogically dividing the storage medium into three regions will be used todiscuss process 200. However, the storage medium can be logicallydivided into fewer or greater number of regions.

Region 1—A region characterized by a fast retrieval value.

Region 2—A region characterized by a medium retrieval value.

Region 3—A region characterized by a slow retrieval value.

Step 206 is forming a classification of files that are to be stored onthe storage medium or are already stored thereon. Process 300 of FIG. 3describes one way of classifying or categorizing files. In process 300,files are classified into three categories: frequently accessed (hot),less frequently accessed (cold), and not accessed within the measurementperiod (frozen). Process 200 is not limited to using these categories.In one embodiment, a fourth category is used for a file which came intoexistence after the start of the measurement period (new file).

Step 208 is storing the files on the storage medium based on theclassification and the retrieval values of the various locations of thestorage medium. Continuing with the example in which three regions areused, files that are categorized as hot are placed into Region 1.Therefore, the files that are frequently accessed are placed in a regionwith a fast retrieval value. Files that are categorized as frozen areplaced in Region 3. Therefore, the files that are infrequently accessedare placed in a region with a slow retrieval value. Files that arecategorized as cold need not be moved at all except when they must bemoved to free up space in region 1, in which case a cold file is placedin Region 2. Therefore, the files that are less frequently accessed tendto be placed in a region with a medium retrieval value.

Example of Categorizing Files

FIG. 3 is a flowchart illustrating steps of a process 300 ofcategorizing files by frequency of access and age, in accordance with anembodiment of the present invention. The ordering of the steps is forconvenience of explanation. Process 300 illustrates a way to place filesinto three categories, but more or fewer categories could be used. Instep 301, file access data is gathered. The gathering of file accessdata is then suspended prior to proceeding with further steps of process300.

In step 302, the age of a particular file is determined, based on thefile access data or otherwise. In step 304, the frequency of access pera particular time period for the particular file is determined byexamining the file access data. For example, the number of times thefile was accessed in the last week is determined. However, other timeperiods can be used.

The time of the last file access is examined to determine if the file isa frozen file. If the last file access occurred more than a thresholdtime in the past, then the file is placed into a category as a frozenfile, in step 308. For example, if the last file access was more thanone month in the past, the file is considered frozen.

If the file is not a frozen file, then the number of file accesses overa period of time is analyzed. If the file was accessed more than athreshold number of times over the time period, then the file is placedinto a category as a hot file, in step 310. As an example, a hot file isone that has been accessed more than a particular number of times in thelast week.

If the file was accessed less than the threshold number of times overthe first time period, then the file is placed into a category as a coldfile, in step 312. A cold file is, for example, a file that has beenaccessed less than the threshold number of times within the last week.

Process 300 refers to various time periods and thresholds. These timeperiods and thresholds may be dynamically adjusted. Process 400 of FIG.4 describes a technique that involves establishing a threshold forplacing files in the hot or cold category.

Classifying files based on access frequency is an example of one way ofclassifying files. However, this is not the only way in which files canbe classified. Another way to classify files is based on events. Still afurther way to classify files is based on data grouping. Moreover, filescan be classified based on any combination of access frequency, events,data grouping, or other factors.

Classifying Files Based on Events

An example of an event is a system boot. In order to increase boot timeperformance of a computer system, files required for booting can beplaced on a fast part of the storage medium during shutdown. The filesare then in the fast or instant part of the storage medium for the bootevent. Once the system is booted the files may be moved to make room forother more pertinent files while the system is up and running. Certainexecutables can also be thus placed on the fast portion of the storagemedium. For example, a frequently-used word processing program or otherdata processing program can be placed in the fast portion of the storagemedium. Rapid launching of such programs makes the computer systemfaster and more responsive to its users.

Classifying Files Based on Data Grouping

Grouping of files or parts of files together on a certain area of thestorage medium can also significantly increase performance. For exampleif you launch a word processor, several different files and/or potionsof files are loaded, additionally data may also be loaded at launch. Ifthe computer has to go to several different areas of the disk to loadthe necessary files or parts of files it will take substantially longerthan if all these files were in the same area on this disk. Furthergrouping folders (directories) with the files they contain will alsospeed up the computer system under certain circumstances. In order todetermine what files to group we merely kept track of what files areread from the disk in sequence. When we can confirm a pattern then thosefiles or portions of files are grouped together.

File Access Monitoring

A File Access Monitor (FAM) is used to track the access frequency ofeach file on a storage medium volume, in accordance with one embodimentof the present invention. This is done in the background on a computer,in real time, while the computer is being used for work, withoutadversely impacting that work. As an example, the FAM can provide thenumber of accesses that have occurred for any file on the system duringthe last day, the last week, the last two weeks, three weeks or fourweeks.

The FAM has an extremely efficient storage method for the accessinformation. This method uses each file's File Record Number as an indexinto the data store. Any file's record can be accessed using its FRN orthe records for all files can be accessed sequentially without requiringthe overhead of record searches or maintaining index lists. Thesestorage methods allow the FAM to work in the background withoutimpacting other system processes.

The FAM uses small, fixed length records that are a whole power of twoin length, in accordance with one embodiment of the present invention.This allows the access methods previously mentioned to be used withoutrequiring time consuming index calculations or requiring logic to handlerecords that span buffers, and it keeps the size of the storagemanageable. Daily and weekly access counts are stored in each record, inone embodiment. Moreover, the data is effectively aged as time passes,without requiring that the data be processed daily or weekly. This isdone by recording a timestamp in each record. When a record is accessed,the current time and the recorded timestamp are used to ripple the datathrough the day and week counters so it reflects the state at that time,and then the timestamp is updated with the current time.

The FAM contains a method to detect file accesses in real-time on anongoing basis for any volume on the computer. This method uses a highpriority thread that repeatedly and continuously requests information onchanges in the directories of a target volume. Any such informationreceived by the thread is queued to a lower priority thread forrecording as described above. The high priority thread handles itsprocessing actions very quickly. Using quick processing and highpriority allows each monitoring thread to capture information about anyand all file accesses while not impacting other processes on thecomputer.

Hardware Overview

FIG. 5 is a block diagram that illustrates a computer system 500 uponwhich an embodiment of the invention may be implemented. Steps ofprocess 300 and process 400 are stored as instructions one or more ofthe computer-readable media of system 500 and executed on the processorof computer system 500. Computer system 500 includes a bus 502 or othercommunication mechanism for communicating information, and a processor504 coupled with bus 502 for processing information. Computer system 500also includes a main memory 506, such as a random access memory (RAM) orother dynamic storage device, coupled to bus 502 for storing informationand instructions to be executed by processor 504. Main memory 506 alsomay be used for storing temporary variables or other intermediateinformation during execution of instructions to be executed by processor504. Computer system 500 further includes a read only memory (ROM) 508or other static storage device coupled to bus 502 for storing staticinformation and instructions for processor 504. A storage device 510,such as a magnetic disk or optical disk, is provided and coupled to bus502 for storing information and instructions. The computer system 500can have any number of processors 504. For example, computer system 500is a multi-processor system, in one embodiment. The processor 504 canhave any number of cores. In one embodiment, the processor 504 is amulti-core processor 504. Computer system 500 can be used in a hyperthreaded machine.

Computer system 500 may be coupled via bus 502 to a display 512, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 514, including alphanumeric and other keys, is coupledto bus 502 for communicating information and command selections toprocessor 504. Another type of user input device is cursor control 516,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 504 and forcontrolling cursor movement on display 512. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

The invention is related to the use of computer system 500 forimplementing the techniques described herein. According to oneembodiment of the invention, those techniques are performed by computersystem 500 in response to processor 504 executing one or more sequencesof one or more instructions contained in main memory 506. Suchinstructions may be read into main memory 506 from anothermachine-readable medium, such as storage device 510. Execution of thesequences of instructions contained in main memory 506 causes processor504 to perform the process steps described herein. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions to implement the invention. Thus,embodiments of the invention are not limited to any specific combinationof hardware circuitry and software.

The term “machine-readable medium” as used herein refers to any mediumthat participates in providing data that causes a machine to operate ina specific fashion. In an embodiment implemented using computer system500, various machine-readable media are involved, for example, inproviding instructions to processor 504 for execution. Such a medium maytake many forms, including but not limited to, non-volatile media,volatile media, and transmission media. Non-volatile media includes, forexample, optical or magnetic disks, such as storage device 510. Volatilemedia includes dynamic memory, such as main memory 506. Transmissionmedia includes coaxial cables, copper wire and fiber optics, includingthe wires that comprise bus 502. Transmission media can also take theform of acoustic or light waves, such as those generated duringradio-wave and infrared data communications. All such media must betangible to enable the instructions carried by the media to be detectedby a physical mechanism that reads the instructions into a machine.

Common forms of machine-readable media include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punchcards, papertape, anyother physical medium with patterns of holes, a RAM, a PROM, and EPROM,a FLASH-EPROM, any other memory chip or cartridge, a carrier wave asdescribed hereinafter, or any other medium from which a computer canread.

Various forms of machine-readable media may be involved in carrying oneor more sequences of one or more instructions to processor 504 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 500 canreceive the data on the telephone line and use an infrared transmitterto convert the data to an infrared signal. An infrared detector canreceive the data carried in the infrared signal and appropriatecircuitry can place the data on bus 502. Bus 502 carries the data tomain memory 506, from which processor 504 retrieves and executes theinstructions. The instructions received by main memory 506 mayoptionally be stored on storage device 510 either before or afterexecution by processor 504.

Computer system 500 also includes a communication interface 518 coupledto bus 502. Communication interface 518 provides a two-way datacommunication coupling to a network link 520 that is connected to alocal network 522. For example, communication interface 518 may be anintegrated services digital network (ISDN) card or a modem to provide adata communication connection to a corresponding type of telephone line.As another example, communication interface 518 may be a local areanetwork (LAN) card to provide a data communication connection to acompatible LAN. Wireless links may also be implemented. In any suchimplementation, communication interface 518 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

Network link 520 typically provides data communication through one ormore networks to other data devices. For example, network link 520 mayprovide a connection through local network 522 to a host computer 524 orto data equipment operated by an Internet Service Provider (ISP) 526.ISP 526 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 528. Local network 522 and Internet 528 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 520and through communication interface 518, which carry the digital data toand from computer system 500, are exemplary forms of carrier wavestransporting the information.

Computer system 500 can send messages and receive data, includingprogram code, through the network(s), network link 520 and communicationinterface 518. In the Internet example, a server 530 might transmit arequested code for an application program through Internet 528, ISP 526,local network 522 and communication interface 518.

The received code may be executed by processor 504 as it is received,and/or stored in storage device 510, or other non-volatile storage forlater execution. In this manner, computer system 500 may obtainapplication code in the form of a carrier wave.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. Thus, the sole and exclusive indicatorof what is the invention, and is intended by the applicants to be theinvention, is the set of claims that issue from this application, in thespecific form in which such claims issue, including any subsequentcorrection. Any definitions expressly set forth herein for termscontained in such claims shall govern the meaning of such terms as usedin the claims. Hence, no limitation, element, property, feature,advantage or attribute that is not expressly recited in a claim shouldlimit the scope of such claim in any way. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

1. A machine-implemented method of accessing one or more storage media,said method comprising the steps of: accessing a retrieval value foreach of a plurality of locations of the one or more storage media;forming a classification of a plurality of files; and storing at least aportion of the plurality of files on the one or more storage media basedon the classification and the retrieval value for each of the pluralityof locations.
 2. The method of claim 1, wherein accessing the retrievalvalue for each of the locations comprises determining the retrievalvalue of each of the locations on the one or more storage media.
 3. Themethod of claim 2, wherein the step of determining the retrieval valueof each of the locations comprises determining an internal transfer ratecharacteristic for each of the locations.
 4. The method of claim 1,wherein forming the classification of the files comprises determiningfrequency of access of at least a portion of the files.
 5. The method ofclaim 4, wherein forming the classification of the files furthercomprises applying a threshold that is adjustable based on frequency ofaccess of files.
 6. The method of claim 1, wherein forming theclassification of the files is based, at least in part, on one or moreevents.
 7. The method of claim 1, wherein forming the classification ofthe files is based, at least in part, on file groupings.
 8. The methodof claim 1, further comprising: dividing the one or more storage mediainto a plurality of regions according to the retrieval value for each ofa plurality of locations, wherein a particular region comprises one ormore of the locations, and wherein the regions are ranked based on theretrieval value for the locations of each particular region; and whereinthe step of storing at least a portion of the plurality of files isfurther based on the ranking of the regions.
 9. The method of claim 1,further comprising: defining a region of the one or more storage mediahaving a range of retrieval value from a fast retrieval value to a slowretrieval value; and wherein the storing at least a portion of theplurality of files is further based on the range of retrieval value. 10.The method of claim 1, wherein forming a classification of the filescomprises receiving user input to prioritize at least a portion of thefiles.
 11. The method of claim 1, further comprising: dividing thelocations into a first region characterized by locations having fastretrieval value, a second region characterized by locations having slowretrieval value, and a third region characterized by locations havingmedium retrieval value; wherein forming a classification comprises:placing files that have been accessed more than a first threshold withina first time period into a first category; placing files that have notbeen accessed for a second period of time into a second category; andplacing files that have been accessed less than the first frequencythreshold within the first time period into a third category; andwherein storing at least a portion of the plurality of files comprises:storing files in the first category in the first region; storing filesin the second category in the second region; and storing files in thethird category in the third region.
 12. A computer readable mediumcarrying one or more sequences of instructions, which when executed byone or more processors, cause the one or more processors to carry outthe steps of: accessing a retrieval value for each of a plurality oflocations of one or more storage media; forming a classification of aplurality of files; and storing at least a portion of the plurality offiles on the one or more storage media based on the classification andthe retrieval value for the plurality of locations.
 13. The computerreadable medium of claim 12, wherein the one or more sequences ofinstructions for accessing the retrieval value for each of the locationsfurther comprise instructions for performing the step of determining theretrieval value of each of the locations on the one or more storagemedia.
 14. The computer readable medium of claim 12, wherein the one ormore sequences of instructions for determining the retrieval value ofeach of the locations comprises one or more sequences of instructionsfor determining an internal transfer rate characteristic for each of thelocations.
 15. The computer readable medium of claim 12, wherein the oneor more sequences of instructions for forming the classification of thefiles further comprise instructions for performing the step ofdetermining frequency of access of at least a portion of the files. 16.The computer readable medium of claim 15, wherein the one or moresequences of instructions for forming the classification of the filesfurther comprise instructions for performing the step of applying athreshold that is adjustable based on frequency of access of files. 17.The computer readable medium of claim 16, wherein the one or moresequences of instructions for forming the classification of the filesfurther comprise instructions for performing the step of forming theclassification of the files based, at least in part, on one or moreevents.
 18. The computer readable medium of claim 16, wherein the one ormore sequences of instructions for forming the classification of thefiles further comprise instructions for performing the step of formingthe classification of the files based, at least in part, on one or morefile groupings.
 19. The computer readable medium of claim 16, furthercomprising instructions which, when executed by the one or moreprocessors, cause the one or more processors to perform the steps of:dividing the one or more storage media into a plurality of regionsaccording to the retrieval value for each of a plurality of locations,wherein a particular region comprises one or more of the locations, andwherein the regions are ranked based on the retrieval value for thelocations of each particular region; and wherein the storing at least aportion of the plurality of files is further based on the ranking of theregions.
 20. The computer readable medium of claim 16, furthercomprising instructions which, when executed by the one or moreprocessors, cause the one or more processors to perform the steps of:defining a region of the one or more storage media having a range ofretrieval value from a fast retrieval value to a slow retrieval value;and wherein the storing at least a portion of the plurality of files isfurther based on the range of retrieval value.
 21. The computer readablemedium of claim 16, wherein the instructions for performing forming aclassification of the files further comprise instructions for performingthe step of receiving user input to prioritize at least a portion of thefiles.
 22. The computer readable medium of claim 16, further comprisinginstructions which, when executed by the one or more processors, causethe one or more processors to perform the steps of: dividing thelocations into a first region characterized by locations having fastretrieval value, a second region characterized by locations having slowretrieval value, and third region characterized by locations havingmedium retrieval value; wherein the instructions for performing forminga classification further comprise instructions for performing the stepsof: placing files that have been accessed more than a first thresholdwithin a first time period into a first category; placing files thathave not been accessed for a second period of time into a secondcategory; and placing files that have been accessed less than the firstfrequency threshold within the first time period into a third category;and wherein the instructions for performing storing at least a portionof the plurality of files further comprise instructions for performingthe steps of: storing files in the first category in the first region;storing files in the second category in the second region; and storingfiles in the third category in the third region.
 23. A system,comprising: a processor; and; computer-readable medium communicativelycoupled to the processor; wherein the computer-readable medium hasstored thereon one or more stored sequences of instructions which, whenexecuted by the processor, cause the processor to perform: accessing aretrieval value for each of a plurality of locations of one or morestorage media; forming a classification of a plurality of files; andstoring at least a portion of the plurality of files on the one or morestorage media based on the classification and the retrieval value forthe plurality of locations.
 24. The system of claim 23, wherein the oneor more sequences of instructions for accessing the retrieval value foreach of the locations further comprise instructions for performingdetermining the retrieval value of each of the locations on the one ormore storage media.
 25. The system of claim 23, The computer readablemedium of claim 7, wherein the one or more sequences of instructions fordetermining the retrieval value of each of the locations comprises oneor more sequences of instructions for determining an internal transferrate characteristic for each of the locations.
 26. The system of claim23, wherein the one or more sequences of instructions for forming theclassification of the files further comprise instructions for performingdetermining frequency of access of at least a portion of the files. 27.The system of claim 26, wherein the one or more sequences ofinstructions for forming the classification of the files furthercomprise instructions for performing applying a threshold that isadjustable based on frequency of access of files.
 28. The system ofclaim 23, wherein the one or more sequences of instructions for formingthe classification of the files further comprise instructions forperforming the step of forming the classification of the files based, atleast in part, on one or more events.
 29. The system of claim 23,wherein the one or more sequences of instructions for forming theclassification of the files further comprise instructions for performingthe step of forming the classification of the files based, at least inpart, on one or more file groupings.
 30. The system of claim 23, furthercomprising instructions which, when executed by the one or moreprocessors, cause the one or more processors to perform: dividing theone or more storage media into a plurality of regions according to theretrieval value, wherein a particular region comprises one or more ofthe locations, and wherein the regions are ranked based on the retrievalvalue for the locations of each particular region; and wherein thestoring at least a portion of the plurality of files is further based onthe ranking of the regions.
 31. The system of claim 23, furthercomprising instructions which, when executed by the one or moreprocessors, cause the one or more processors to perform: defining aregion of the one or more storage media having a range of retrievalvalue from a fast retrieval value to a slow retrieval value; and whereinthe storing at least a portion of the plurality of files is furtherbased on the range of retrieval value.
 32. The system of claim 23,wherein the instructions for performing forming a classification of thefiles further comprise instructions for performing receiving user inputto prioritize at least a portion of the files.
 33. The system of claim30, further comprising instructions which, when executed by the one ormore processors, cause the one or more processors to perform: dividingthe locations into a first region characterized by locations having fastretrieval value, a second region characterized by locations having slowretrieval value, and third region characterized by locations havingmedium retrieval value; wherein the instructions for performing forminga classification further comprise instructions for performing: placingfiles that have been accessed more than a first threshold within a firsttime period into a first category; placing files that have not beenaccessed for a second period of time into a second category; and placingfiles that have been accessed less than the first frequency thresholdwithin the first time period into a third category; and wherein theinstructions for performing storing at least a portion of the pluralityof files further comprise instructions for performing: storing files inthe first category in the first region; storing files in the secondcategory in the second region; and storing files in the third categoryin the third region.